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How Many Servers Do I Need?

by Rupert Davey15 January 2015

This is an interesting question as there is no right answer. Every business and every IT system is different. Here are some good rules of thumb and some things to keep in mind when deciding how many servers you need.

Factors to consider

Your company will have client machines, normally computers running Microsoft Windows, and those machines will have users. You may have those users scattered over several sites and working from home.

Depending on how these users access your centralised data, such as your company email, your shared files and your line of business applications, will go some way to dictating how many servers you need.

There's also considerations such as the number of sites you operate. A site may require a dedicated server just as a connection end point for the network.

Client machines and their users require management. This could be from a Microsoft Active Directory or other centralised management suites. These need servers and all the client machines need some form of connectivity, either directly, over a VPN or via the cloud.

Virtual host servers count too. Even though they'll be doing a dedicated task, they will still need support and maintenance from time-to-time.

And finally, you may follow the "one server per service" rule, which says that each network service has its own server. For example, files have their own server, antivirus management has its own server etc. This is fairly unlikely in a small business as although these services can be split out for scalability it's often not necessary with low numbers of users.

The golden ratio

Over the last ten plus years, in my travels through the world of IT, the ratio of 10 users per server has remained a pretty good guide.

For every 10 users of the IT system you should have one server. This is obviously only a very broad statement. There's no detail about what that server does or where it lives.

In the real world a business with an average demand on their IT systems (files, emails, internet access and a couple of line of business applications) will have between eight and 12 users per server.

You may now be doing a quick count and if you come out with the following, here are the sorts of things to consider further:

Too many

You have too many servers per person. At the extreme this is more servers than people! If this is the case, you probably don't have an average demand on your IT systems.

More likely is you're in the one server per five users camp; plus or minus one or two servers. If this is the case, you have "server sprawl". Someone in the past may have been throwing hardware at a problem due to lack of knowledge about migrating to new platforms.

Are all those servers needed? Do you know what they all do? Are they all backed up? Are they all physically secure? Do they all have manufacturer's warranties? Are they all patched? Are all your servers correctly licenced? As you can see, asking those questions of three servers is much easier than asking them of 15 servers!

Too few

You've done your count and you're in the one server per 30, 40 or 50 users camp! Excellent. Well, be careful here too. With so few servers per person, is all the company data in a central location? Are all the client machines managed? Is all the data secure? Are you spending on pay-as-you-go applications where an on-premises solution would be more cost effective?

There is not one answer for every business. Some companies may require a large number of servers, and some may operate a specific business model with fewer servers where the users are charged with the management of their own machines. However, do think about how many you have and weigh up the pros and cons. There may be savings to be made in reduced costs, reduced risks and increased agility.